The use of light emitting diodes (LEDs) in lighting devices is increasing. LEDs are now common in various lighting devices, such as televisions, lamps, headlights and automotive infotainment displays, for example.
A feature commonly found in lighting devices is the dimming features. As is known, the human eye perceives brightness levels logarithmically. To make dimming appear to be even to the human eye a dimming engine changes the dimming levels in an exponential manner over time. For example, to make the change in brightness to be perceived by a human eye as a linear change, the signal controlling the LEDs, such as a pulse width modulation (PWM) signal, is changed in an exponential manner.
A conventional approach to dimming includes the use of an exponential law conversion stage that stores an exponential conversion law. The exponential law conversion stage converts linear variations in the input into exponential variations in the output. The output of the exponential law conversion stage is used to, e.g., to generate a PWM signal to drive the LEDs. The exponential law conversion stage may be implemented with a look-up table (LUT) stored in memory, for example.
In some applications, it may be desirable to use different conversion laws at different times. In such applications, a conversion stage includes multiple conversion laws, which may or may not include the exponential conversion law.